The semiconductor structures disclosed herein relate to lateral double-diffused metal oxide semiconductor field effect transistors (LDMOSFETS) and, more particularly, LDMOSFETS having a relatively deep, fully-depleted, drain drift region for providing ballasting resistance.
Typically, an LDMOSFET, like a conventional MOSFET, comprises a channel region positioned laterally between a source region and a drain region. However, unlike the conventional MOSFET, the LDMOSFET is asymmetrical. Specifically, the drain region of the LDMOSFET is separated from the channel region by a relatively low-doped drain drift region, which provides ballasting resistance so that the LDMOSFET has a relatively high blocking voltage (i.e., a high maximum voltage that can be applied to the transistor). However, as operating voltages and device densities increase, LDMOSFETs with even higher blocking voltages and better transistor-to-substrate and/or transistor-to-transistor isolation are needed to prevent device failures.